Polygonal fasteners having milled slots



Dec. 10, 1968 E. J. SKIERSKI 3,415, 5

JOLYGONAL FASTENERS HAVING MILLED S LOTS Filed Feb. 2. 1967 Inventor:

fdwm J. Skiers/(1' United States Patent 3,415,154 POLYGONAL FASTENERS HAVING MILLED SLOTS Edwin J. Skierski, Wayne, N.J., assignor to Parker-Kalon Corporation, Clifton, N.J., a corporation of Delaware Filed Feb. 2, 1967, Ser. No. 613,550 4 Claims. (Cl. 85-9) ABSTRACT OF THE DISCLOSURE A wrench engageable polygonal fastener portion such as a screw head or a nut having a milled screw driver slot in which the sides of the polygon are concave to provide space in which burrs resulting from the milling of the slot may lie without interfering with the engagement of the wrench.

This invention relates generally to improvements in polygonal wrench engageable fastener portions such as screw heads and nuts and more particularly to such portions which include milled slots.

It is common practice during assembly operations to drive sheet metal screws having hexagonal heads with a power driver having a socket embracing the complete contour of the head. For convenience in maintenance it is preferable that such heads be slotted to receive the blade of a screw driver for disassembly. In order to obtain the best possible appearance of the screw head as a whole as well as to provide a slot which maintains its engagement with the screw driver blade, the preferred form of slot is milled rather than of slightly tapered shape which results when the slot is formed at the same time as the head of the screw by a cold heading process. Accordingly, automatic machines have been designed for milling slots in such screws.

A problem arises, however, in that the milling of the slot produces burrs at the exit end of the slot, that end last engaged by the teeth of the slotting saw. Such burrs thereafter often interfere with the proper engagement of the driver employed in production operations. When the whole heighth of the head is of uniform shape the burr may be successfully removed by a tumbling operation. But this does require an additional operation and thereby adds to the cost of the product. However, when the head is of the so-called integral washer type in which a part of the head is not polygonal but circular in cross section, the burrs formed in milling are much less accessible to tumbling grit and can therefore not be reliably removed by this expedient.

It is accordingly an object of the invention to provide a fastener shape applicable to screw heads and nuts in which burrs generated in milling slots need not be removed and yet will not interfere with the driving engagement of a driver socket.

A further object is to reduce the cost and improve the overall quality of fasteners having polygonal wrench engageable surfaces without adding to the cost of the product.

In the achievement of the foregoing objects a feature of the invention relates to the formation of a concavity in each of the sides of the polygonal wrench engageable portion of a fastener. The slot is then so oriented that the exit end of the slot, approximately bisects the side at the deepest point of the concavity. The burr resulting at the exit end of the slot from the milling operation accordingly lies within the concavity without interfering with a socket which drives by the engagement largely with the corners of the polygonal portion.

The objects and features of the present invention will be best understood from an illustrative embodiment of the 3,415,154 Patented Dec. 10, 1968 invention taken in connection with the accompanying drawings in which:

FIG. 1 is a plan view on a greatly enlarged scale of a sheet metal screw having a head formed according to the present invention;

FIG. 2 is a view partly in longitudinal section of the screw of FIG. 1;

FIG. 3 is a plan view of a flanged castell-ated nut contoured according to the present invention; and

FIG. 4 is a view partly in longitudinal section of the nut of FIG. 3.

Turning now to the drawings there is shown in 'FIGS. 1 and 2 a sheet metal screw having a hexagonal head, indicated generally at 10, in which a slot 12 has been milled. The screw of FIGS. 1 and 2 is of the washer head type including a washerlike flange 14, a factor which presents special problems in the removal of burrs resulting from slot milling. As seen in FIG. 2 the bottom of the slot indicated at 16 is arcuate as a result of the direction of feed along the axis of the screw toward the slotting saw. In addition it may be seen from FIGS. 1 and 2 that the slotting saw was rotated in the clockwise direction about a center to the left of the screw head as shown in FIG. 2 and in line with the axis of the screw. The result of the direction of rotation of the slotting saw is that a burr 18 is formed along the sides of the slot 12 and a burr 20 along the bottom of the slot at the exit end of the slot, that is, the end last contacted by the teeth of the slotting saw as it emerges from the screw head.

In order to avoid possible interference between the burrs 18 and 20 and a six pointed socket for driving the screw the burrs 18 and 20 would conventionally be removed by tumbling. Such action tends to mar the finish of the head and is an added operation in the manufacture of a product made in huge quantities and sold at very low prices. Because of the presence of the flange 14, however, the burr 18 near the bottom of the slot and the burr 20 are not readily removable by the tumbling action. In the case of screw heads formed without the flange 14 the removal of the burrs is more readily accomplished by tumbling.

The need for removal of the burrs 18 and 20, which are greatly exaggerated in the drawings for purposes of clarity, is obviated by forming a concavity 22 in each of the sides 24 of the head. The sides 24 intersect to define angles or corners 26 which provide the main driving engagement with the socket of the driving tool. It will be appreciated, of course, that while FIGS. 1 and 2 are drawn on a greatly enlarged scale for clarity a typical screw head of the illustrated type may normally be on the order of 4" across the flats 22 and the corresponding difference between the dimension across the flats and across opposite corners 26 does not permit a wide allowance for fit between the head dimension and the interior of the socket. The depth of the concavity 22 is accordingly subject to variation according to the size of the screw head, being shallower in smaller screws and being made progressively deeper as the screw size is increased until a suffi:

'cient depth of concavity is reached to accommodate the burrs produced under extreme conditions of speed, feed and saw condition. As shown in FIG. 1 the concavity 22 is limited as is the case in larger screw sizes to the midportion of each side 24. This limited extent of concavity is preferable in that each of the corners 26 is defined by flat lands which more exactly fit the driving sockets. However, in the smaller screw sizes it has been found that the concavity may be in the form of a gentle curve extending from corner to corner and without a flat land while producing an acceptable fit of the screw head in the driver.

The same principle is applied to a castellated flanged nut 28 shown in FIGS. 3 and 4 in which the flange is indicated at 30. Above the flange 30 the nut 28 is of generally hexagonal shape and three slots 32 are milled connecting the approximate midpoints of opposite sides of the hexagon. Each of the slots 32 has at its exit end a side burr 34 and a bottom burr 36. As in the case of thet slot 12 in the screw head 10, the slots 32 are individually milled, the nut being fed along its axis toward the slotting saw revolving in a clockwise direction about a center to the left of FIG. 4 with the result that the bottom of each ;slot is arcuate and the burrs 34 and 36 are produced at that end of the slot last engaged by the teeth of the saw. The burrs resulting from the milling of slots may be removed by tumbling when the nut is of uniform cross section without the flange 30. However, in the case of flanged nuts the bottom burr 36 is particularly difficult to remove reliably.

The need for removal of the burrs 34 and 36 is eliminated by forming in each side of the nut 28 a concavity 37. It is assumed here that the nut is cold formed as in the case of the screw head 10. Under these circumstances the concavities 37 are obtained by appropriate shaping of the interior of the cold forming die and at very little if any increase in, cost over a straight-sided die. Because the smallest castellated nuts in general use are of considerably larger size than the smaller screw heads of the type depicted in FIGS. 1 and 2, it is preferable and can be readily afforded in the case of nuts to have a flat land at each end of each side so to define each corner or angle 38. This more conventional corner is readily engaged by a 12 pointed socket which is frequently employed for loosening and tightening nuts. At the same time the concavity 36 provides a space for the burrs 34 and 36 without interfering with the driving engagement of a six pointed socket.

The invention has been described to this point as applied to hexagonal fastener portions, screw heads and nuts, be it will be readily appreciated that the concavity may be similarly formed in the straight sides of a square head or one having any even number of sides. It is also applicable to polygonal shapes having an odd number of sides so long as the polygon is so located that the exit end of the slot approximately bisects a concave side and that the slot extend from a corner to the midpoint of the opposite side.

Having thus described my invention what I claim as new and desire to secure by Letters Patent of the United States is:

1. A fastener having a generally polygonal wrench engageable portion of an even number of sides characterized by the fact that each of the sides of the polygonal portion is formed with an exterior concavity in at least the midpoint of a part of its extent and further comprises at least one milled slot extending between approximate midpoints .of a pair of the diametrically opposed sides having its exit end intersecting the concavity in one of said opposed sides whereby a burr formed at the exit end of the slot is contain'ed within the concavity without interfering with the driving engagement of a wrench.

2. A fastener according to claim 1 in which the fastener is a screw and in which the polygonal wrench engageable portion is hexagonal and comprises at least a part of a head.

3. A fastener according to claim 2 characterized by the fact that the head also includes in addition to the hexagonal portion a washer like flange presenting an obstruction to the expedient removal of the burr.

4. A fastener according to claim 1 in the form of a castellated nut characterized by the fact that the nut is formed at its lower end with a circular flange presenting an obstruction to the expedient removal of the burr.

References Cited UNITED STATES PATENTS 2,543,705 2/1951 Place 859 3,013,598 12/1961 Marcy. 3,129,742 4/1964 Faroni et al 1515 3,277,942 10/ 1966 Dwyer 8532 CARL W. TOMLIN, Primary Examiner.

R. S. BRITTS, Assistant Examiner.

US. Cl. X.R. 85-32, 

